Hydraulic cylinders of the aforementioned kind are known, for example, from the publications DE A1 22 38 211 and DE-A1 40 02 558 and are used in hydraulically operated or controlled devices, in particular, as working cylinders. This kind of connection between cylinder pipe and cover or bottom is simpler and less expensive to produce than such connections as screw thread, soldered or welded connections. This feature also offers advantages particularly with respect to mass produced articles.
In the case of these known hydraulic cylinders, the cylinder pipe is constricted by simply bending or beading and thus fits into a groove provided on the circumferential surface of the bottom or cover. This results in a particularly unreliable connection and is not very suitable for high working pressures. In the case of another known hydraulic cylinder, one side of the groove-shaped recess is designed in the shape of a truncated cone. The related end of the cylinder pipe is pressed into this recess through compressive deformation in such a manner that the material of the cylinder pipe forms an annular segment resting against the bottom in the region of the groove, and subsequently a conical segment resting against the conical surface. The drawback with this arrangement is that with higher stress the cylinder pipe can slip at least partially over the conical surface, resulting in at least a leak if not failure.
The object of the present invention is to improve a hydraulic cylinder of the aforementioned kind in such a manner that the aforementioned drawbacks of the known arrangements are avoided. More particularly, it is an object of the present invention to provide a more reliable connection between cylinder pipe and cover or bottom despite a simpler and less expensive production.